Separation of ruthenium from aqueous solutions



United States Patent 3,202,479 SEPARATION OF RUTHENIUM FROM AQUEOUS SOLUTIONS Joseph J. Katz, Chicago, 11]., assignor to the United States 7 Patented Aug. 24, 19 65 and nitric acid, are suitable. Studies made on the concentration of the acid showed that the results of the process are not impaired by changes of the molarity.

The process of this invention is particularly advanof America as represented by the United States Atomic tageous in the solvent extraction process for the sepy 'C9mmlS5 l011 v a aration of uranium and plutonium from fission products. N0 -12 2 2, 1 2% 1- In this process ruthenium, which is a fission product, aims has always been a complicating factor because it is ex- This invention deals with the separation of ruthenium tracted together with uranium and with plutonium and values from aqueous solutions and in particular with the diflicult to separate therefrom. This fact made it necesvolatilization of' ruthenium values from aqueous acid sary for complete separation to apply a great number of solutions in the form of ruthenium tetroxide. solvent extraction cycles. This disadvantage is overcome It is an object of this invention to provide a process by the process of this invention, since practically the enfor eliminating ruthenium values from aqueous solutions tire amount of the ruthenium may be removed prior to which does not necessitate addingof a substantial amount solvent extraction. Anotherinstance where this process of foreign ions so that no undesirable reaction products 'has utility is in the precipitation of plutonium with a are formed in the solution by the reaction. carrier precipitate from aqueous solutions. Also there This and other objects are accomplished by treating it is useful to remove the ruthenium prior to precipita-' the ruthenium-containing aqueous solution, in the prestion. ence of an oxidation catalyst, with ozone whereby the The process of this invention is useful in the removal ruthenium is oxidized to ruthenium tetroxide and volaand recovery of ruthenium values from aqueous solutilized as such. tions obtained by the leaching of ruthenium-containing A great number of catalysts have been found suitable ores. for the process of this invention. For instance, substances In the following table, a number of experiments are containing permanganate anions, dichromate anions, compiled which show the operativeness of the process silver cations, cerium (IV) cations, cobalt cations, nickel and in particular the criticalness of the use of a catalyst.

Table I Flow rate of 02 EN O3 con- Catalyst Time of Ruthenium containing 1% centration, Ruthenium ozonization, volatilized, ozone, (am/min. N content hrs. percent Type Gone, M

60 5 3x10 cts./cc./min 6 8 so 5 0.01 d 0 27 60 5 0.01 30 00 1400 5 0. 025 2 94 1400 5 0.001 2 99 1400 5 0. 001 do 2 70 1400 0. 3 0. 025 0.1 mg./l. plus 10. 1. 5 99. 7

cts./cc.lmin. 1400 o. 1 0. 025 2. 5 99. 7 1400 0.8 0. 025 2. 5 99. 1 1400 0.8 0. 025 s. 7 99. 7 840. 0. 1 0. 025 4 99. 2 1400 0. 1 0. 01 3. 5 99. 1, 1400 0. 3 0. 025 1. 5 99 1400 0.3 0.025 s so 1400 0.1 0. 001 5 59 cations, periodate anions, bromate anions and lead dioxide have given very good results. Molarities of these catalysts ranging from 0.001 to 0.1 have been used with satisfaction.

While heating of the solution from which the ruthenium is to be removed is not necessary and, in fact, mostly does not show any advantage over treatment at room temperature, an elevated temperature up to 90l00 C. has been found preferable in the case that uranium and/or plutonium values are present in the solution.

The ozone is preferably introduced in diluted form, for instance in admixture with oxygen, air, nitrogen or the like. Concentrations of from 0.5 to 5% of ozone in All runs illustrated in this table were carried out atv room temperature. It will be seen from this table that in the first experiment, where no catalyst was used, only 8% of ruthenium had been volatilized as ruthenium tetroxide after an ozonization time of six hours, while in the second experiment, which was carried out under identical conditions except for the presence of silver ions at a concentration of 0.01 M, 27% of the ruthenium was removed.

The application of the process of this invention to the removal of ruthenium from solvent extraction feed solutions and from dissolver solutions obtained by dissolving neutron-irradiated uranium slugs, in other words, to solutions containing uranyl nitrate or other uranium salts and plutonium salts, is illustrated in Table II. A few preliminary tests which, for the sake of comparison, were carried out with a uraniumand plutonium-free ruthenium solution, are also included in this table.

T able II Cone. of Catalyst Cone. of Type of Cone. of O in 02, Flow rate Time of Tempera- Ruthenium uranium, ruthenium nitric percent of gas, ozonizature, C. volatilized,

M acid, N by wt. cc./min. Type Ccfic tion, hrs. percent 0. 3 5 300 NazCrzOL 0. 025 2 25 92 0. 3 5 300 NazCrzO 0. 025 5 25 96 0.3 5 300 115105---- 0.025 2 25 95 0.3 0. 5 3100 AgNO3. 0. 025 2 25 99. 8 0.3 0.5 3100 Ce (IV). 0.025 1 25 95 0.3 1 1400 AgNO3 0.025 2 25 99. 7 0.3 0. 5 1400 Ce (IV 0.025 2 25 99 2 0.3 0. 5 3100 Ce (IV)- 0.025 2 95 84 2 0. 3 0. 5 3100 Ce (IV).. 0. 025 12 05 93 2 0. 3 0. 5 3100 KMnO4 0. 001 5 95 96 2 0.3 0. 5 3100 KM11O4. 0. 001 12 95 97 2 0. 3 5 3000 AgNOa 0. 025 12 95 98 2 0.3 5 3000 AgNOa 0. 025 20 95 99 2 0.3 5 1500 KM11O4.-. 001 12 100 98 2 0.3 3000 KBrOa- 0.1 8 100 98 2 2 1 1400 None 2. 5 50 55 Ozonator walls were cooled which reduced distillation of R1104.

The uranyl nitrate concentration, as obvious from the Q 5. The process of claim 4 wherein the diluent gas is table, ranged from 0 to 2 M. The ruthenium removal from the solutions containing uranium was considerably slower than from the uranium-free aqueous solutions; however, a fairly complete removal may also be obtained in the presence of uranium as is obvious from the experiments which yielded a ruthenium volatilization of 99% and more.

While there have been described herein certain specific embodiments of the invention, limitation to the details given is not intended, and modifications may be made within the spirit of the disclosure and the scope of the appended claims.

What is claimed is:

1. A process for separating ruthenium values from aqueous acid solutions, which comprises adding an oxidation catalyst to said solutions and introducing ozone in a concentration of at least 0.5% by weight thereinto whereby ruthenium tetroxide is formed and volatilized.

2. The process of claim 1 wherein the maximum temperature at which the process is carried out is 90 C.

3. The process of claim 2 wherein a diluent gas is used for carrying the ozone.

4. A process for separating ruthenium values from acidic aqueous solutions, which comprises adding an oxidation catalyst to said solutions to provide a concentration of 55 0.001 to 0.1 M and introducing a mixture of at least 0.5% by weight of ozone and a diluent gas thereinto whereby ruthenium tctroxide is formed and volatilized.

oxygen.

6. The process of claim 4 wherein the diluent gas is nitrogen.

7. The process of claim 4 wherein the diluent gas is air.

8. The process of claim 4 wherein the oxidation catalyst is permanganate anion.

9. The process of claim 4 wherein the oxidation catalyst is silver cation.

10. The process of claim 4 wherein the oxidation catalyst is cerium (IV) cation.

11. The process of claim 4 wherein the oxidation catalyst is dichromate anion.

12. The process of claim 4 wherein the mixture of ozone and a diluent gas is introduced into the solution while at room temperature.

References Cited by the Examiner Hayhurst et al.: Journal of the Chemical Society, vol. 97, pp. 868-877 (1910).

Rulf et al.: Zeitschrift fiir anorganische Chemie, vol. 136, PP- 49-61 (1924).

MAURICE A. BRINDISI, Primary Examiner.

JAMES L. BREWRINK, Examiner. 

1. A PROCESS FOR SEPARATING RUTHENIUM VALUES FROM AQUEOUS ACID SOLUTIONS, WHICH COMPRISES ADDING AN OXIDATION CATALYST TO SAID SOLUTIONS AND INTRODUCING OZONE IN A CONCENTRATION OF AT LEAST 0.5% BY WEIGHT THEREINTO WHEREBY RUTHENIUM TETROXIDE IS FORMED AND VOLATILIZED. 